The tote board at the Pleasant Hills Sheetz station on Clairton Boulevard advertising fill-ups for $1.99 a gallon looks too good to be true. In fact, for most motorists, it is.

The sign is for a fuel known as E85, a lower-polluting blend of 15 percent gasoline and 85 percent corn-based ethanol that's sold only at a handful of stations and meant for a relatively small number of cars and trucks known as flexible-fuel vehicles.

Even so, with the price of regular unleaded hovering around $2.70 a gallon, some drivers with regular cars are finding E85 and its price tag too hard to resist. "We run into people saying, 'I don't care what it's doing to my car. It's a lot cheaper, so I'm using it,' " said Monica Jones, spokeswoman for the Altoona-based convenience store chain.

It's not hard to understand why E85 can be so tempting. Prices at the pump for regular unleaded gasoline have shot up about 50 cents a gallon over the last two months, and with the busy summer driving season approaching, there's no letup in sight.

Locally, a gallon of regular unleaded was averaging $2.70 a gallon yesterday, up nearly 10 cents in the last week alone, according to AAA East Central motor club.

One big contributor fueling the run-up has been the rising cost of crude oil, which has climbed from about $50 a barrel in January to the mid-$60 range, even after falling $1.30 yesterday amid easing tensions between Britain and Iran.

Adding to the price pressures is the fact that this is the time of year oil refiners typically scale back to perform maintenance and make other changes in preparation for summer.

The lull in production, which is expected to be unusually long this year, crimped inventories at the same time oil imports have been falling from Europe, which is straining to keep up with increased worldwide demand, said Laurie Falter, oil industry economist with the Energy Information Administration.

Pump prices are projected to peak this spring at about $2.75 a gallon nationwide around Memorial Day, Ms. Falter said, then flatten out before peaking again in late July or early August as demand jumps at the height of the vacation driving season.

For now, administration analysts are not estimating how high prices will go this summer, she said.

The last two summers, prices peaked at around $3 a gallon nationwide.

"It's safe to say prices are going to be at least that high" this summer, Ms. Falter said. "They aren't going to be lower."

That could boost demand for E85, even if it's not advisable to use the fuel in most cars.

"If we see someone without a flexible-fuel vehicle trying to fill up, we come out and tell them that we don't recommend it," said Ms. Jones, the Sheetz spokeswoman. Using E85 a couple of times, "probably won't cause major damage," she said. "But long-term use could be corrosive to your engine."

Sheetz posts a list of the makes and models that can take E85 at the special corn-cob topped pumps, which also have stickers warning customers that using the fuel in non-flex-fuel vehicles could cause engine damage and void the manufacturer's warranty.

In addition, some motorists don't realize that E85 cuts gas mileage by up to about 25 percent compared to regular gas, so, depending on the price difference, any savings can be lost by having to fill up more often.

Local outlets that sell the blend include the Pleasant Hills site and stations on Campbells Run Road in Robinson and William Penn Highway in Monroeville.